miRNA-27b-3p and miRNA-1228-3p correlate with the progression of Kidney Fibrosis in Diabetic Nephropathy

Diabetic Nephropathy (DN) is a chronic complication of diabetes and the primary cause of end stage renal disease. DN can be differentially diagnosed only through histological investigation. Therefore, there is need for molecular biomarkers, such as miRNAs, to discriminate among different histological lesions in diabetics. Aim of this study was to identify a pattern of differentially expressed miRNAs in kidney biopsies of DN patients and to assess their potential as differential diagnostic biomarkers. Using microarray, we assayed miRNA expression in kidney tissue from 8 DN patients, 6 diabetic patients with membranous nephropathy and 4 patients with normal histology. Nine miRNAs were differentially expressed among the three groups of patients, thus underlying their potential role as markers of specific histological damage. In silico we identified 2 miRNAs (i.e., miR-27b-3p and miR-1228-3p) showing an interaction with UBE2v1, an ubiquitin-conjugating E2 enzyme variant that mediates the formation of lysine 63-linked ubiquitin chains, a mechanism we showed as involved in DN kidney fibrosis. Both miRNAs were confirmed to be down-regulated in DN biopsies, using qPCR and in situ hybridization, and in urines of DN patients. Interestingly, the urinary levels of both miRNAs were also able to discriminate among different degrees of renal fibrosis. Finally, we showed that the combined urinary expression of both miRNAs was also able to discriminate DN patients from other glomerulonephritides, both in the presence and absence of T2D. We identified two regulatory miRNAs potentially useful as diagnostic biomarkers of tubular-interstitial fibrosis in diabetic patients with DN. A total of 16 RNA samples were employed in this study: 6 samples were taken from patients with type 2 diabetes (T2D) and biopsy-proven diabetic nephropathy (DN); 6 samples were taken from patients with T2D and biopsy-proven membranous nephropathy (T2D-MN); and 4 samples were from normal kidney (CTRL) patients who underwent kidney biopsy.